The Constant Sum plugin is a Custom Interfaces format built on the constant sum base type. It's a distinct plugin storage twin from the native Constant Sum question documented in Grid & Allocation Questions — same allocate-to-a-total concept, but with a touch-optimized entry UI.
What respondents see#
A running total in a bottom bar and a grid of items respondents tap or press-and-hold to increment toward a shared total. Values can render as a plain number, a percentage, or with a currency symbol.
When to use it#
- Budget-allocation or share-of-wallet questions on mobile, where the desktop constant-sum grid is too fiddly to tap through.
Configuring it in the builder#
Drag Constant Sum from the Custom Interfaces group in the question palette. Items are authored the same way as the native Constant Sum question's rows. Plugin-specific behavior lives in the question's Settings tab.
Settings reference#
| Setting | What it controls | Default |
|---|---|---|
| Question text tooltip | Shows the full question text as a hover tooltip on the header | Off |
| Max total | The total respondents allocate to | 100 |
| Step size | Increment per tap / long-press tick | 5 |
| Seconds to reach maximum | Long-press duration to traverse 0 → max total | 4 |
| Answers to show | If > 0, only render the first N items | 0 (all) |
| Total enforced | Hide Next until the total equals max total | Off |
| Enforce total as maximum | Hard-clamp each item so the running total can never exceed max | On |
| Show total | Display the running total in the bottom bar | On |
| Show as percentage | Render values as "n%" instead of a plain number | Off |
| Currency symbol | $, £, €, ¥, ₣, ₹, or None (ignored if showing percentage) | None |
| Show end decimals | Force two decimal places | Off |
| Answers display | Image only, text only, or both | Both |
| Instructions in popup | Where the description surfaces (neither/desktop/mobile/both) | Neither |
| Desktop popup width | Instruction popup width on desktop, as a percentage | 60% |
| Press-and-hold hint | Inline "Tap or Press & Hold" instruction text toggle | Off |
| Box padding | Inner padding of each item card (px) | 1 |
| Mobile scroll hint text | Hint shown above the scroll arrows on mobile | Blank |
| Fit to screen | Clamp the scroll area to the viewport | On |
| Font size / desktop adjustment | Base text size + desktop bump | 17px / +4px |
| Max characters / digits | Direct-entry input limits | 300 chars, 8 int / 12 decimal digits |
| Button & message text | Review-instructions label, running-total label, confirm button text, and the max-total-exceeded alert (maxTotal placeholder) — edited on the Messages and text tab | Customizable |
Logic support#
Built on constant sum, so it supports the same allocation-total condition operators as the native Constant Sum question. See Logic, Flow & Conditions.
Good to know#
- Don't confuse this with the native Constant Sum question — they share the same underlying data shape but the plugin swaps in a different respondent widget with its own settings.
Related guides#
- Question Types — overview and when-to-use table
- Custom Interfaces — all 22 custom interface formats
- Grid & Allocation Questions — the native Constant Sum question
- Logic, Flow & Conditions — operators and condition builder
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